According to the development of a service toward convergence between a broadcasting service and a communication service, multimedia services provided through various media are being universalized. That is, a service using an existing broadcasting media such as a ground-wave, a satellite, or a cable has been diversified based on a digital scheme, and at the same time, convergence services such as mobile broadcasting services such as a Digital multimedia broadcasting (hereinafter, referred to as “DMB”) service, a Digital Video Broadcasting-Handheld (hereinafter, referred to as “DVP-H”), and an Advanced Television Systems Committee-Mobile/Handheld (hereinafter, referred to as “ATSC-M/H”) service, and an Internet Protocol Television (hereinafter, referred to as “IPTV”) service have appeared. Especially, digital broadcasting provides a program having a picture dozens of times clearer than existing analog broadcasting, a sound quality which is a Compact Disk (hereinafter, referred to as “CD”) level and provides many more channels, thereby providing opportunities for a wide selection, a new bidirectional service such as home shopping, home banking, e-mail, Internet and a high-grade broadcasting service.
Meanwhile, in order to provide a digital broadcasting service, various types of signaling information are required. The signaling information may be divided into two primary types, for example, service acquisition (hereinafter, referred to as “Service Acquisition”) information and service announcement (hereinafter, referred to as “Service Announcement”) information. Each of the service acquisition information and the service announcement information will be described below.
The service acquisition information includes information required by a reception apparatus to physically receive a digital broadcasting service. For example, the information may be information required to receive service configuration information and a media component.
The service announcement information is information which is used in a case of selecting a digital broadcasting service by a reception apparatus, and provides additional information with respect to the digital broadcasting service. For example, the service announcement information may include a service genre, service schedule information, and a synopsis.
Meanwhile, the signaling information may be generally transmitted through a data link layer or an application program layer, and a type of signaling information transmitted in each of transmission layers may be changed according to an individual broadcasting standard. Generally, in consideration of a transmission bandwidth and a channel mapping time, only the minimum signaling information which is required for a digital broadcasting service reception and a digital broadcasting service selection is transmitted through the data link layer. In contrast, much more signaling information is transmitted through the application program layer, compared to the data link layer.
Meanwhile, signaling information transmitted through the data link layer is transmitted by using a signaling table structure, and various types of signaling tables are used according to an individual broadcasting standard. However, in the case of transmitting signaling information through the data link layer, all signaling information in a single signaling table is not stored and transmitted. Instead, a plurality of signaling tables are generated according to each purpose, and the signaling tables are associated with each other based on an Identifier (hereinafter, referred to as “ID”) information, so as to form a hierarchical structure for transmission. For example, representative signaling tables used in a moving picture experts group-2 (MPEG-2) transport stream (TS) (hereinafter, referred to as “MPEG-2 TS”) standard include a program association table (hereinafter, referred to as “PAT”) storing service configuration information included in a TS and a program map table (hereinafter, referred to as “PMT”) storing media component configuration information of an individual service. The two tables may be interconnected by using an attribute of “program_number”. That is, in order to obtain detailed information with respect to an arbitrary service X, additional information with respect to an individual media component of the service X may be acquired by analyzing a PMT having an identical “program_number”, using a “program_number” of a service X obtained through the PAT.
In addition, a scheme of defining a separate signaling table according to each purpose and providing a hierarchical structure formed through mutual contact between corresponding signaling tables has an excellent effect when the number of services included in a transmission stream is large, in comparison with the flat structure scheme using a single independent signaling table for transmission. For example, when there are a large number of services and media components which constitute an individual service, if all signaling information is stored in a single signaling table and thus a size of a corresponding signaling table increases, ultimately, a time which is required to receive the corresponding signaling table in a reception apparatus increases. In addition, in this case, when signaling information is changed, a time which is required to update a signaling table due to a change of the signaling information also increases. In addition, in a case of maintaining an individual signaling table according to each purpose, it is advantageous for management side of signaling information in a transmitter.
However, if a transmission stream is composed of a small number of services, a single signaling table structure may be more effective. That is, when a transmission stream is composed of a small number of services, although signaling information is integrated with a single signaling table and then transmitted, since a size of a signaling table increases enough to provide a sufficient transmission/reception performance, performance degradation due to reception of the signaling table may be minimized in a reception apparatus side. Meanwhile, a processing complexity of a reception apparatus may be reduced since all information may be acquired from the reception of the single signaling table.
As described above, a hierarchical structure scheme and a flat structure scheme have different merits and demerits according to characteristics of a service configuration.
However, in a general digital broadcasting system, only a hierarchical structure has been used in constituting signaling information. Accordingly, use of a flat structure having the merits as described above has not been completely considered.